ABSTRACT
Most theoretical efforts of granular dynamics start by considering the fluidized granular medium as a dense, inelastic gas with a temperature defined by local velocity fluctuations (Bagnold 1954; Jenkins and Savage 1983). However, there are two particularly important aspects that contribute to the unique properties of granular materials: ordinary temperature plays no role, and the interactions between grains are dissipative because of static friction and the inelasticity of collisions. In order to reveal the underlying nature of the dynamical processes, the velocity autocorrelation function (VAF) is a key quantity from which basic transport properties can be calculated. Its knowledge gives the understanding of macroscopic properties in terms of single grain dynamics.
